package pdd;

import java.util.Scanner;

public class T1 {

    public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);

            int n = sc.nextInt();
            int result = 0;
            while (n>0) {
                n--;
                int temp = sc.nextInt();
                result += Math.abs(temp);
            }
            System.out.println(result);
    }
}
